Abstract: This Improved Rotary End Cutting Tool is a completely new concept in twist-drill theory, design, and method of construction. Which will revolutionize the rotary end cutting tool systems as presently known today; especially in larger drill (30) diameters. The new concept of an incurvate cutting-edge (38), purposely orchestrated and offset volumetric grooves (41) combined with a tapered residual core-area (50) in the forward conical forward-end, along with all other renovative improvements. Has virtually resolved drill-chatter, rapid dulling, poor centering, penetration, and even breakage; naming just a few from a list of problems inhabiting currently marketed twist-drills (30). With the overall combined improvements, being to extensive to list herein, having afforded a uniquely simple insert cutting-unit (47) displaying a fixed and removable version capable of equally performing as well as its one-piece counterpart twist-drill (30).